It is difficult to predict how multiple sclerosis will progress in any one person. Most people with MS will be able to continue to walk and function at their work for many years after their diagnosis. The factors associated with the mildest course of MS are being female, having the relapsing-remitting form, having the first symptoms at a younger age, having longer periods of remission between relapses, and initial symptoms of decreased sensation or vision rather than of weakness or incoordination.

Less than 5% of people with MS have a severe progressive form, leading to death from complications within five years. At the other extreme, 10-20% have a benign form, with a very slow or no progression of their symptoms. The most recent studies show that about seven out of 10 people with MS are still alive 25 years after their diagnosis, compared to about nine out of 10 people of similar age without disease. On average, MS shortens the lives of affected women by about six years, and men by 11 years. Suicide is a significant cause of death in MS, especially in younger patients.

The degree of disability a person experiences five years after onset is, on average, about three-quarters of the expected disability at 10–15 years. A benign course for the first five years usually indicates the disease will not cause marked disability.